Method and apparatus for improving ink-jet print quality using a jittered print mode
A computerized method for improving ink-jet print quality. A jittered print mode is instigated to scatter print errors having a cyclic cause, viz., patterns of visibly noticeable artifacts or dot arrangements caused by mechanical misalignments and vibrations and electrical tolerance variations that are cyclic in nature. A jitter of ink droplet firing time is intentionally introduced whereby printed dot placement is offset less than a dot diameter. The jitter algorithm is adaptable to a variety of implementation schemes.
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Claims
1. A computerized method for scattering cyclic print error in an ink-jet hard copy apparatus from at least one ink-jet print head having a plurality of ink drop firing nozzles scanned across a print medium while printing rows and columns of dots on said print medium, comprising the steps of:
- during a sweep of said print head wherein a plurality of ink drops are fired in dot matrix rows and columns during a predetermined section of said sweep, introducing a varied alteration of time of ink drop firing during each said sweep such that each dot is shifted less than one dot width.
2. The method as set forth in claim 1, said step of introducing a varied alteration of time of firing further comprising the steps of:
- determining time of firing of each ink drop during a print head position encoder cycle,
- introducing a varied selected shift to said time of firing.
3. The method as set forth in claim 2, said step of introducing a varying selected shift index further comprising the steps of:
- introducing a selected shift of time of firing such that drop placement is shifted.+-.one-eighth dot row.
4. The method as set forth in claim 2, said step of introducing a varying selected shift index further comprising the steps of:
- introducing a varying selected shift of time between each time of firing.
5. The method as set forth in claim 2, said step of introducing a varying selected shift index further comprising the steps of:
- introducing a varying selected shift of time between each encoder cycle.
6. The method as set forth in claim 2, said step of introducing a varying selected shift index further comprising the steps of:
- introducing a varying selected shift of time between each scan.
7. The method as set forth in claim 2, said step of iintroducing a varying selected shift index further comprising the steps of:
- introducing a varying selected shift of time variedly during each scan.
8. An ink-jet hard copy apparatus, comprising:
- an input for receiving a print medium;
- a carriage mounted for scanning across a received print medium;
- at least one ink-jet printing cartridge mounted in said carriage for firing ink drops onto said received print medium to create dots thereon;
- means for encoding movement and position of said cartridge during scanning across said received print medium;
- general computer memory means having a program for calculating time of firing of ink drops onto said received print medium and for jittering said firing of ink drops such that time of firing is shifted.+-.a predetermined amount.
9. The apparatus as set forth in claim 8, said program further comprising:
- said predetermined amount produces a dot shift maximum of approximately one-eighth dot row.
10. The apparatus as set forth in claim 8, said program further comprising:
- jittering using a timing jitter index generator.
11. The apparatus as set forth in claim 8, said program further comprising:
- said time of firing is shifted said predetermined amount for each drop firing within an encoding cycle.
12. The apparatus as set forth in claim 8, said program further comprising:
- said time of firing is shifted a different amount during each drop firing within an encoding cycle.
13. The apparatus as set forth in claim 8, said program further comprising:
- said time of firing is shifted a different amount after each encoding cycle.
14. The apparatus as set forth in claim 8, said program further comprising:
- following each scan of said received print medium.
15. A general computer memory having a program for scattering ink-jet drop placement on print media comprising:
- means for determining the time it takes an ink-jet print head to travel during one movement and position encoding cycle;
- means for determining time of firing of each set of ink drops during said one movement and position encoding cycle; and
- means for shifting the time of firing during scanning the print head across the print media such that ink drops land in a zone encompassing a target pixel center.
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Type: Grant
Filed: Jun 9, 1997
Date of Patent: Aug 10, 1999
Assignee: Hewlett-Packard Company (Palo Alto, CA)
Inventors: Mark Garboden (Vancouver, WA), Jason Quintana (Vancouver, WA)
Primary Examiner: Arthur G. Evans
Application Number: 8/871,127
International Classification: G06K 1500;
